Evaluation of sugar beet planting dates variation based on climatic parameters in different regions in Kermanshah province

Determination of sugar beet planting date is one of the important factors influencing field management. The occurrence of frost damage after seedling emergence has been considered as a limiting factor for early sugar beet planting. This study was conducted to determine the proper sugar beet planting date in Islamabad Gharb, Kangavar and Kermanshah (including Sahne, Bisotun, and Mahidasht cities). A model was designed based on meteorological data collected from 1993 to 2008. After running a normality test for soil and meteorological data (Shapiro-Wilk test), the probability of temperature decrease (less than -2 oC) under different months (from March to May) was determined using normal distribution function. Then, according to the required base-temperature and thermal units from planting to emergence as well as collected temperature data at the depth of 5 cm in each region, the plausible planting and emergence time was predicted. Through combining the probability of frost occurrence (less than 20%) at -2 oC and proposed planting date and field emergence, a plating-time model was developed for each region. Results showed that the average thermal units required from planting to seedling emergence was 173 growing degree days for all regions. Based on the results, the earliest planting date with minimum frost damage for Kermanshah, Islamabad Gharb, and Kangavar are 17th March, 22nd March, and 9th April, respectively.